Cleaning metals and preventing them from corroding.



JAMES H. GRAVELL, F PHILADELPHIA, PENNSYLVANIA.

. ham onnrb' CLEANING METALS AND PREVENTING THEM FROM CORRODING.

1,221,4ld1l.

No Drawing.

To all whom it may concern:

' fication.

This invention relates to cleaning metals,

I especially steel, and its object is to clean steel so that it will not rust or metal so that it will not corrode. The invention will be described in connection with steel but its use is not limited to that metal.

Steel and iron are now cleaned by the action of various acids, such as sulfuric, hydrochloric and nitric. The acids are diluted with ten times their volume of water and the solution thus formed is held in large non metallic tanks and kept at a boiling temperature. The work to be cleaned is placed in this boiling solution for about fifteen minutes. On removing the work which has been cleaned by the action of the solution, it is necessary to neutralize the acid solution remaining on the surface of the work by dipping the work into a bath of lime water, as otherwise the Work would immediately rust. It is very diflicult, however, to get rid of all of the acid even after dipping the work into the'lime water and it is well known thatsteel' or iron that has been subjected to the action of such an acid is more liable to rust than if it has not been so treated. I

This rusting and this tendency to rust is decidedly objectionable from a commercial.

standpoint. I have discovered, however, that this objectionable feature of cleaning steel r by a chemical bath can be entirely avoided acid for this purpose but that material is entirely too expensive for rough commercial work and its use has been restricted to fine classes of products, such as steel furniture and automobile bodies. The material I use, however, is very inexpensive and is not prohibited by its cost from being applied to rough castings, hot rolled steel and the like. To make a chemicalbath according to my invention, I use approximately seventeen pounds of hydrocalcium phosphate to ten gallons of water and raise the temperature of'this bath to the boiling point andimmerse Specification of Letters Patent.

the material to be cleaned in the bath for about fifteen minutes. All these proportions and the time I allow the bath to act on the work are approximate as the bath will act quicker if I make it stronger and the time taken to clean the work naturally depends on how corroded or dirty the work is.

Hydrocalcium phosphate is made commercially by treating calcium phosphate (in the form of bone-ash or some phosphate rock) Patented Apr. 3, 19ft.

Application filed November 15, 1916. Serial No. 131,394.

in water with sulfuric acid to form hydrocalcium phosphate and calcium sulfate. The calciumsulfate precipitates and the hydrocalcium phosphate dissolves in the water. The precipitate is separated from the solution and the solution evaporated to a semiliquid mass of hydrocalcium phosphate.

The reaction above referred to may be eX-' pressed as follows:

when evaporated to a semi-liquid state, is ,more readily soluble in water and therefore best adapted for making my bath.

It is immaterial to the success of my bath .whether the hydrocalcium phosphate is added to water or whether the hydrocalcium phosphate is made in the water by adding to it calcium phosphate andan acid such as sulfuric acid, as the calcium sulfate formed by the latter method does not in anyway interfere with the action of the bath on the immersed metal. When I make abath by the latter method, I use, for example, enough phosphate rock or bone-ash to supply twentyfive pounds of calcium phosphate, and fourteen pounds of sulfuric acid to ten gallonsof water.

In cases where the transportation of acid liquid is objectionable, the acid may be replaced by an acid'salt capable, when placed in water, of reacting with the calcium phosphate to form hydrocalcium phosphate. Sodium acid sulfate is a good example of ,such an acid salt and it reacts with calcium phosphate, in an aqueous solutlon as follows:

As calcium phosphate and sodium acid on each other when not in contact with water, they may be mixed together to form a dry admixture which can be stored until required for use or may be conveniently transported to where the bath is required, without danger of leaking or evaporation.

YMy bath acts in a similar way to the well known sulfuric acid pickle by removing scale, rust, corrosion and the like from the surface of steel'and iron, but has the distinct advantage over the sulfuric acid pickle in that it does not cause the metal to subsequently rust. The work may be withdrawn from my solution or bath and allowed to drain and dry and need not be subjected to the action of lime to neutralize the remain-' ing acid on' the surface. The work treated bymy bath and thbn allowed to drain and dry is practically rust-proof it kept indoors.

The surface, however, remains sticky for, some time which for some work 1s ob ectionable. This can be remedied, however, by

dipping in a second bath similar to the first,

except that it contains about five times as. much water, in" other words, in a weak solution of hydrocalcium phosphate. The surface now will dry very quickly and be free from sticldness.

When my bath acts on iron or steel for a short time, such as fifteen minutes, it has a cleaning action as I have already described;

but when it is allowed to act on the .work for a much longer time, say several hour's, it has 'thepeculiar and meritorious property of depositing on the surface of the iron or steel a coating of substantial thickness, firmly attached to the metal. I have found that ma-- j terial on which this coating has'been formed I 1 by my bath is practically rust-proof even. 40

when exposed to the weather. f This coating is a medium gray in color bu can be made a very dark gray or nearly black sult that the'coating assumes a very dark.

mixture of ironand manganese phosphates.-

e0 l-Iydroca'lcium'. phosphate contains calcium 7 by adding manganese dioxid to my'bathin about'the proportion of-one pound of manganese dioxid to every ten pounds of hydrocalcium phosphate used. As manganese dioxid is a dry powder-and has no action on either dry calcium phosphate or dry sodium acid sulfate, it may be added to the dry ad-" mixture of these two materials which I have already described. During the described dis- .solving' action of the hydrocalcium phos- 'phate on the work, the manganese dioxid is converted into manganese phosphate whichis precipitated out of the bath onto the work along with the iron phosphate, with the regray or black appearance and consists of a and it may well be that this calcium operates to oppose the solution the bath of phosing.

I ing it from corroding and water.

'phate of iron formed on the work and so promotes the formation of the coating to which reference has been made.

' Iam familiar with the 'atents issued to T. W. Cqslett which-descri e a method of producing a coating with phosphoric acid and I do not wish to claim anythin disclosed .by him but my bath is muc less tage that it. does not have to be evaporated to one-seventh of its volume as is the case with Coslettin fact Ido not have to evaporate my bath to an noticeable extent to produce my coating. other advantage of my bath over that of Coslett is, that'my bath both cleans and forms a coating, whereas Cosletts will not clean but only forms a coat- I do not claim specifically a bath or ingredient for a bath consisting of an admixture of'calci'um phosphate, water, andan acid salt capable of reactingwith the same to form hydrocalcium phosphate, nor the method which involves theuse thereof, since those matters are the sub'ect-matter of' my divisional application, erial No.'138,992', filed December 26th, 1916. I

What I claim is:

1. A bath for cleaning metal and' reventconsisting 0 an' admixture of calcium p sists in treating the metal with an admixture of calcium phosphate, sulfuric acid and water.

5. The method of cleaning steel and iron and preventing it from rustin which consists in treating the metal wit an admixture of hydrocalcium-phosphate, manganese dioxid and water.

6. The method of treating metal which consists in immersing it in a heated bath containing' hydrocalcium phosphate fora period .of time suflicient to clean it, substantially as described.

7. The method of treating metalwhich consists in immersing it in afheated bath containing hydrocalcium phosphate for a period of time suflicient to both clean and coat it,

substantially 'a's described.

- J. H. GRAVELL.

osph ate, sulfuric 'acid of an ad- 70 costly to make and has the decided ad van 

